To continue, using our model of cerebrovascular spasm, the study of the prostaglandins, their antagonists, and other drugs and constituents of blood in the clinic and laboratory in determining the cause, prevention and treatment of cerebrovascular spasm. To investigate the role of platelet inhibition in laboratory induced cerebral infarction and vasospasm and in a careful clinical trail to test sulfinpyrazone, a platelet inhibitor, as a prevention of stroke. To use radioactive microspheres in determining regional and total cerebral blood flow in various vascular syndromes. To investigate the prevention or amelioration of the edema of a cerebral infarction by studying the various physical and chemical factors affecting the infarct edema. Bibliographic references: Experimental study on the genesis of cerebral vasospasm. White, R.P., Hagen, A.A., Morgan, H., Dawson, W.N., and Robertson, J.T. Stroke 6:52-57, 1975; Role of prostaglandins in cerebrovascular tone. White, R.P. Prostaglandins 9: 405-407, 1975.